<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script type="text/javascript">
        var arr = new Array(1,3,4,5,6,7,8,9);
        var orun=arr.indexOf(12);
        alert(orun)

    </script>
</head>
<body>

<pre>
    var arr = new Array();
    arr[0]=1;
    arr[1]=3;
    arr[2]=5;
</pre>
</body>
</html>